1. Field of the Invention
The present invention relates to a rig which can efficiently and economically drill wells at virtually any angle, from nearly horizontal to vertical. More particularly still, the present invention relates to a rig which can efficiently and economically drill wells, including deviated or high angle wells, with less pipe stress and impact on the surrounding environment than conventional drilling rigs.
2. Description of the Prior Art
Many wells, such as oil and/or gas wells are drilled vertically into the earth's crust. However, it is frequently beneficial to drill wells at an angle from vertical. Such “deviated” wells are often drilled from a single surface location towards one or more subsurface targets which are situated some lateral distance away from said surface location. In many cases, such deviated wells are intentionally oriented to penetrate one or more subterranean formations at a desired angle from vertical.
Frequently, wells are drilled vertically at the earth's surface, and thereafter deviated in a different direction—that is, a desired angle from vertical—at some point down-hole. In other situations, it is often desirable to drill a deviated well at an angle from vertical starting at or very near the earth's surface. Specialized slant rigs have been developed for such wells. Unlike standard drilling rigs which typically have fixed vertical derricks, such specialized slant rigs have derricks which can be tilted from vertical. Most existing slant rigs can tilt from horizontal to approximately 30 degrees, or from vertical to about 45 degrees. However, such existing rigs cannot slant at virtually any angle between 0 and 90 degrees—that is, from nearly horizontal to vertical.
Such conventional slant rigs suffer from a number of shortcomings. Most notably, such rigs do not have lifting, pulling or pushing capacity comparable to standard drilling rigs having stationary, vertical derricks. As a result, such conventional slant rigs are not able to drill deep wells, and/or wells that have a significant lateral component.
Thus, it is an object of the present invention to provide a rig that can drill deviated wells at an angle from vertical. It is yet another object of the present invention to provide a rig having significant lifting capacity that can drill deviated wells to depths which are comparable to those drilled by standard larger capacity drilling rigs.